x2 sudo commands cannot be executed in terminal

Question

I am running a Ubuntu system on my Radxa Zero 3E (single board computer)

Using its GPIO I am driving a 5V LED via an NPN transisitor. Everything works.

For switching it on I use gpioset $(gpiofind PIN_36)=1 & for off gpioset $(gpiofind PIN_36)=0

My question is I cannot run above commands as a single line like sudo gpioset $(gpiofind PIN_36)=0 I must first move to root terminal via sudo su & then commands work perfectly.

The other alternative is that I use x2 separate sudo one liners first for gpiofind & then for gpioset. Both Binaries are located in /usr/bin

Answer 1

As I inferred from OP's follow-up to my comment that my guess is probably right, I'm posting this as an answer.

The problem here is that in sudo gpioset $(gpiofind PIN_36)=0, only gpioset is executed as root. The shell evaluates the substitution by executing gpiofind PIN_36 before executing the surrounding command, so that is executed as whoever started the shell, which is also why it works in a shell started by root.

The fix is just to add sudo in front of the "inner" command, so the command becomes sudo gpioset $(sudo gpiofind PIN_36)=0.